Method of jetting print material and method of printing

ABSTRACT

A method of printing a three-dimensional object. The method includes: supplying a print material to a plurality of ejector conduits arranged in an array, the ejector conduits comprising first ends configured to accept the print material and second ends comprising ejector nozzles; advancing the print material in one or more of the ejector conduits of the array until the print material is disposed in the ejector nozzle of the one or more ejector conduits; heating the print material positioned in at least one of the ejector nozzles using radiant energy, the heating causing at least a portion of the print material to be ejected from the at least one of the ejector nozzles and onto a print substrate; and repeating both the advancing the print material and the heating the print material to form a three-dimensional object on the print substrate.

DETAILED DESCRIPTION Field of the Disclosure

The present disclosure is directed to a printer jetting mechanism thatcan be employed in printers used for additive manufacturing (referred toherein as three-dimensional (“3D”) printers). The present disclosure isalso directed to methods of jetting print material, including methods of3D printing.

Background

Melting of solid materials, including materials in the form of solidfilaments, is commonly used in 3D printing techniques. It is wellunderstood that when phase change or heating of a material occurs, thematerial generally expands and, in the case of phase change from solidto liquid, becomes flowable. Print materials are often melted to allowflow of the material and deposition onto a substrate in order to form a3D object therefrom. As a specific example, liquid three-dimensionalprinters for building 3D objects from molten aluminum are known in theart. One such 3D printer is disclosed in U.S. Pat. No. 9,616,494. The 3Dprinter works by using DC pulses applied by an electromagnetic coil toexpel molten aluminum drops in response. A platen to which the drops aretargeted translates to allow for the drops to be connected and built upto produce a three-dimensional object. However, drops of molten aluminumejected from this 3D printer have diameters of ˜0.5 mm or larger. Thisenables high volume throughput metal part fabrication. However, therelatively large drop size can result in an undesirable degree ofporosity of 3D objects printed thereby, as well as uneven build surfacesduring fabrication, unwelded drops, and shape inconsistencies. All ofthese potentially lead to degraded physical properties such as poortensile strength, as well as poor appearance issues with the finalobject and/or the inability to print objects with very fine details.

Therefore, methods and systems for improving the quality ofthree-dimensional objects made from three-dimensional printers, such as,for example, liquid metal printers, would be a step forward in the art.

SUMMARY

An embodiment of the present disclosure is directed to a method ofprinting a three-dimensional object. The method comprises: supplying aprint material to a plurality of ejector conduits arranged in an array,the ejector conduits comprising first ends configured to accept theprint material and second ends comprising ejector nozzles; advancing theprint material in one or more of the ejector conduits of the array untilthe print material is disposed in the ejector nozzle of the one or moreejector conduits; heating the print material positioned in at least oneof the ejector nozzles using radiant energy, the heating causing atleast a portion of the print material to be ejected from the at leastone of the ejector nozzles and onto a print substrate; and repeatingboth the advancing the print material and the heating the print materialto form a three-dimensional object on the print substrate.

Another embodiment of the present disclosure is directed to a method forjetting print material from a printer jetting mechanism. The methodcomprises: supplying a print material to a plurality of ejector conduitsarranged in an array, the ejector conduits comprising first endsconfigured to accept the print material and second ends comprisingejector nozzles; advancing the print material in one or more of theejector conduits of the array until the print material is disposed inthe ejector nozzles of the one or more ejector conduits; and heating theprint material positioned in at least one of the ejector nozzles usingradiant energy, the heating causing at least a portion of the printmaterial to be ejected from the at least one of the ejector nozzles.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the present teachings, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentteachings and together with the description, serve to explain theprinciples of the present teachings.

FIG. 1 illustrates an example of a printer jetting mechanism, accordingto an embodiment of the present disclosure.

FIG. 2 illustrates a top view of a printer jetting mechanism, accordingto an example of the present disclosure.

FIG. 3 illustrates a bottom view of an ejector nozzle having an innerwidth (e.g., diameter), d_(i), according to an embodiment of the presentdisclosure.

FIG. 4 illustrates a top view of a printer jetting mechanism comprisingcolumns of ejector conduits that are staggered, according to anembodiment of the present disclosure.

FIG. 5A illustrates a schematic, cross-sectional view of an ejectorconduit with a print material therein that can be employed in theprinter jetting mechanisms described herein, according to an embodimentof the present disclosure.

FIG. 5B illustrates a schematic, cross-sectional view of the ejectorconduit of FIG. 5A, after vaporization of a portion of the printmaterial and ejection of another portion of the print material below thevaporized portion, according to an embodiment of the present disclosure.

FIG. 6 illustrates a schematic, cross-sectional view of an ejectorconduit comprising a vent, according to an embodiment of the presentdisclosure.

FIG. 7A illustrates a schematic, bottom view of an ejector nozzlecomprising a plurality of vents, according to an embodiment of thepresent disclosure.

FIG. 7B illustrates a schematic, cross-sectional view along line A-A ofa portion of an ejector conduit 106 that includes the ejector nozzle ofFIG. 7A, according to an embodiment of the present disclosure.

FIG. 8 is a block diagram of a 3D printer, according to an embodiment ofthe present disclosure.

FIG. 9 is a flow diagram of a method for jetting print material from aprinter jetting mechanism, according to an embodiment of the presentdisclosure.

FIG. 10 illustrates a schematic side view of a printer jetting mechanismcomprising a plurality of ejector conduits simultaneously ejectingdroplets to print a 3D object on a print substrate, according to anembodiment of the present disclosure.

FIG. 11 is a schematic view of a 3D printer, according to an embodimentof the present disclosure.

It should be noted that some details of the figures have been simplifiedand are drawn to facilitate understanding of the embodiments rather thanto maintain strict structural accuracy, detail, and scale.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the presentteachings, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals have been usedthroughout to designate identical elements. In the followingdescription, reference is made to the accompanying drawings that form apart thereof, and in which show by way of illustration specificexemplary embodiments in which the present teachings may be practiced.The following description is, therefore, merely exemplary.

The present disclosure is directed to a printer jetting mechanismcomprising a plurality of ejector conduits arranged in a jet array, aswell as a 3D printer employing the printer jetting mechanism. Methods ofemploying such a jetting mechanism for jetting print material are alsodisclosed. The printer jetting mechanism is designed to employ a radiantenergy induced expansion of the print material as the force for jetting,as will be described in greater detail herein. The jetting mechanism, 3Dprinter and methods of printing disclosed herein can provide one or moreof the following advantages: the ability to selectively jet printmaterial comprising a wide range of metals and other materials; theability to jet selectable droplet volumes; the ability to jet smalldroplet sizes that enable printing of fine and/or selectable featuresizes; and the ability to print at relatively high throughputs.

Printer Jetting Mechanism

FIG. 1 illustrates an example of a printer jetting mechanism 100,according to an embodiment of the present disclosure. The printerjetting mechanism 100 optionally comprises a feeder mechanism 102 foradvancing a print material 104 to be printed. Exemplary printingmaterials 104 are pre-formed wires of selected alloys, or othermaterials as will be discussed in greater detail below. A plurality ofejector conduits 106 are arranged in an array 107. Each ejector conduit106 comprises a first end 106A positioned to accept the print material104 from the feeder mechanism 102. A second end 106B comprises anejector nozzle 108. FIG. 2 illustrates a top view of the printer jettingmechanism 100. A passageway 106C defined by an inner surface of each ofthe ejector conduits 106 allows the print material 104 to pass throughthe ejector conduits 106 from the first end 106A to the second end 106B.As also illustrated in FIG. 2 , the printer jetting mechanism furthercomprises a plurality of radiant energy sources 110 for emitting radiantenergy 112. The plurality of radiant energy sources 110 are positionableso that a path of radiant energy 112 emitted from one or more of theplurality of radiant energy sources 110 is capable of striking theejector nozzle 108 of each of the plurality of ejector conduits 106during operation of the printer jetting mechanism 100. Referring to FIG.2 , the plurality of radiant energy sources 110, which can be lasers(e.g., laser pixels in a laser array) or any other source of radiantenergy suitable for providing thermal energy to the ejector nozzle, areswitched on or off as desired to heat the print material 104 in theejector nozzle 108 to achieve a rapid expansion of the print material.The rapid expansion of print material can include a phase change (e.g.,melting) of the print material or can be accomplished by expansion ofthe material in a single phase. Examples of lasers that can be employedas radiant energy sources 110 include fiber laser arrays or scanned andmodulated lasers, which can provide suitable pulses of radiation for thedesired expansion of the print material and which are well known in theart.

The radiant energy sources 110 can be chosen to emit radiation at anywavelength that is suitable for providing the desired thermal energy toachieve expansion of the print material. The particular wavelengthsemployed will depend on the type of print materials used, among otherthings. Examples of suitable wavelengths range from ultraviolet (“UV”)wavelengths to near infrared (“NIR”) wavelengths, such as about 300 nmto about 1500 nm. As another example, the wavelengths range from about600 nm to about 1100 nm.

Referring to FIG. 3 , the ejector nozzle 108 has an inner width (e.g.,inner diameter), d_(i), which ranges in size, for example, from about 10microns to about 1000 microns, from about 20 microns to about 500microns, from about 50 microns to about 200 microns, or about 100microns. In an embodiment, d_(i) ranges in size from about 10 microns toabout 100 microns, such as about 10 microns to about 50 microns, orabout 10 microns to about 25 microns. While the cross-sectional shape ofthe ejector passageway is illustrated as being a circle having adiameter, d_(i), it is noted that any other cross-sectional shape can beemployed, such as, for example, a rectangle or other polygon, oval orother shape. The inner width for cross-sectional shapes other than acircle is the widest cross-sectional dimension (e.g. the diagonalbetween two opposite vertices of a square cross-section), where thecross-section lies in a plane that is perpendicular in all directions tothe longitudinal axis, “/”, (FIG. 1 ) of the passageway 106C at thepoint where the cross-section intersects the passageway 106C. If thereis more than one possible value for d_(i) (e.g., such as if the valuefor d_(i) varies along the length of the ejector nozzle 108), then thed_(i) is the smallest of the possible d_(i) values for the ejectornozzle 108. Although “inner width” is often referred to as “innerdiameter” herein, the term “diameter” or “inner diameter” can bereplaced by “inner width” when discussing the ejector nozzle's innerdiameter throughout this disclosure.

The ejector nozzles 108 can be an end portion of the ejector conduits106 that is positioned to be exposed to the radiant energy 112 fromradiant energy sources 110 during operation of the printer jettingmechanism 100. A length of the ejector nozzle 108 can range, forexample, from about 1 to about 10 times the inner width (e.g., innerdiameter). The design and materials of the ejector nozzles 108 can bethe same as or different than the remaining portion of the ejectorconduits 106.

In an embodiment, passageway 106C of the ejector conduits 106 has asecond inner width at the first end 106A, the second inner width beingwider than the inner width, d_(i), of the ejector nozzle 108 in order toallow the print material to be easily threaded into the first end 106A,while allowing passageway 106C to closely fit around print materialwithin the ejector nozzle 108. In an embodiment, the passageway 106C cangradually taper from the second inner width to the inner width of theejector nozzle 108 to avoid print material 104 in the form of a solidfilament from being caught in and/or undesirably blocking the passageway106C.

The feeder mechanism 102 can by any suitable mechanical system, pressuredriven system or other system capable of feeding print material 104 tothe ejector conduits 106. The feeder mechanisms can comprise one or morepumps, actuators or combination thereof that can function as a mover 102a (FIG. 11 ) for moving the print material 104. Examples of suitableactuators include electric motors, piezo electric motors, inchwormactuators, hydraulic actuators, and pneumatic actuators. The type offeeder mechanism 102 that is used will depend on the type of printmaterial 104 being employed. In an example, print material 104 comprisesa plurality of filaments and the feeder mechanism 102 is a mechanism foradvancing the plurality of filaments. The term “filament” or “filaments”for purposes of the present disclosure is defined to include both solidwire-like filaments or liquid filaments, such as liquid filledcapillaries or other liquid filled conduits. Examples of feedermechanisms for solid filaments include spool feeders and inch wormactuators, which are well known in the art. Other feeder devices forratcheting or otherwise advancing solid print material 104 to theejector conduits 106 in the form of solid filaments, dry powders orother solid forms can also be employed as the feeder mechanism 102, aswould be understood by one of ordinary skill in the art.

In embodiments, the feeder mechanism 102 can be any suitable mechanismfor supplying a liquid print material, such as a liquid filament, intothe ejector conduits 106 and advancing the liquid print material to theejector nozzles 108. Examples of suitable feeder mechanisms for liquidprint materials include mechanisms employing capillary forces and/oroverpressures sufficient to advance the liquid from a reservoir or othersource of print material (e.g., molten metal) and thereby stably refillthe ejector nozzles 108 after ejection occurs (e.g., the feedermechanism can be designed to automatically refill the ejector nozzlesafter an ejection occurs). The feeder mechanisms 102 can comprise, forexample, a pump, a feeder conduit and/or print material reservoirconfiguration that can be filled with print material to provide ahydrostatic pressure head (e.g., by maintaining a certain fill level ofprint material in the reservoir), or any other device for applyingoverpressure. Such feeder mechanisms are well known in the art. One ofordinary skill in the art would be able to readily determine anappropriate feeder mechanism.

In an embodiment, the feeder mechanism 102 can supply the print materialto each ejector conduit 106 at a different feed rate. As an example, afeeder mechanism 102 for advancing the plurality of filaments comprisesa separate mechanism for incrementally advancing each of the pluralityof filaments at a separately controllable feed rate. Thus, in anembodiment, as the ejection rate at each ejector is increased ordecreased as desired for printing, the feed rate is able to satisfyreplenishment of print material 104 to the ejector nozzles before thenext ejection.

The plurality of ejector conduits 106, including the ejector nozzles108, can comprise any material that can withstand jetting processtemperatures, which will vary widely depending on the print material 104to be printed, while maintaining desired structural integrity and energytransfer properties, such as light absorbing and/or light transmittingproperties. In an embodiment, the material is a refractory material. Forpurposes of the present disclosure, the terms “refractory material” and“refractory materials” are broadly defined as any materials that have amelting point of 1000° C. or more at 1 atmosphere pressure. For example,the refractory material can have a melting point ranging from 1000° C.to about 4000° C., such as about 1200° C. to about 4000° C., or about1400° C. to about 3500° C., or about 1700° C. to about 3500° C., orabout 2000° C. to about 3500° C. Ejector conduit materials can havemelting points outside of these ranges. For example, where the printmaterial 104 is a polymer, ejector conduits can potentially be made ofmaterials with melting points lower than 1000° C., such as 800° C., 700°C., 500° C. or lower. The material employed for the ejector conduits 106can be chosen from materials, such as refractory materials, that aretransparent to the radiation 112, materials, such as refractorymaterials, that absorb the radiant energy 112, or a combination thereof.

Referring to FIG. 1 , the ejector conduits 106, including the ejectornozzles 108, can comprise a transparent material 114 that allows theradiation 112 to be transmitted through the sidewall of the ejectorconduit to directly strike the print material 104, according to anembodiment of the present disclosure. The transparent material 114 cancomprise any material that has both the desired transparency andrefractory properties, which may depend on the wavelength of theradiation 112 and the print material expansion temperatures, among otherthings. Examples include materials chosen from doped or undopedamorphous silica (e.g., fused silica) and sapphire. In an embodiment,the sidewalls of the ejector conduits 106 can be designed so that thetransparent material 114 will refract excess portions of the radiantenergy 112 that strike the sides of the ejector conduit 106 but thatwould otherwise miss the print material 104, so that the excess portionsare redirected toward a portion of the passageway 106C within theejector nozzle 108 so as to strike the print material 104 duringoperation of the printer jetting mechanism 100. For example,cylindrically shaped glass ejector conduits 106 can act as a lens torefract light inward so that the light strikes a reflective surface(e.g., ejector housing 120) at the back side of the ejector conduit 106.The reflective surface can then focus the light into the inner diameterof the ejector conduits 106 so that the light can strike the printmaterial 104.

In another embodiment, the ejector conduits 106, including the ejectornozzles 108, comprise a combination of transparent and absorbingmaterials, such as where at least a portion of each of the plurality ofejector conduits 106 comprises a material, such as a refractorymaterial, suitable for absorbing the radiant energy and converting it tothermal energy in an amount sufficient to cause an expansion of theprint material in the ejector nozzle 108. An example of such anembodiment is illustrated in FIG. 2 , which shows the plurality ofejector conduits 106 comprising a layer of transparent material 114,which can be any of the transparent materials as described above, and alayer of optical absorption material 116 that is suitable for absorbingthe radiant energy 112. The layer of optical absorption material 116 isdisposed, for example, so as to form the inner surface of the pluralityof ejector conduits 106. Any material that has the desired radiationabsorption properties and refractory properties can be employed. Forexample, the layer of optical absorption material 116 can comprise atleast one material chosen from diamond-like carbon, graphite, blackchrome and black alumina. The layer of optical absorption material 116can have any suitable thickness that provides the desired thermal energyto the print material 104. As an example, the thickness can beapproximately equal to the optical absorption length of the material atthe wavelength of radiant energy 112. Thicker layers can also beemployed, although thickening may reduce the amount of heat energytransferred to the filament material. Examples of thicknesses range fromabout 10 nm to about 10000 nm, such as about 25 nm to about 1000 nm, orabout 50 nm to about 500 nm, or about 100 nm.

Other configurations can also be employed for the ejector conduits 106.In an embodiment, the ejector conduits 106, including the ejectornozzles 108, can comprise an absorbing material 116 alone, without thetransparent material 114. For example, the entire ejector conduit 106can potentially comprise a thin-walled metal conduit with high thermalconductance, such as copper, copper alloys, refractory metals or othermetals with a suitably high thermal conductance and melting point forthe printing application.

While the entire ejector conduit, including the ejector nozzles 108, cancomprise the same materials, in an alternative embodiment the ejectornozzle 108 can comprise different materials than other portions of theejector conduit 106. For example, the ejector nozzle can comprise atransparent material 114 that allows the radiation 112 to strike theprint material 104, while the remaining portion of the ejector conduit106 can comprise a material, such as a refractory material, that is nottransparent, such as graphite, platinum, platinum alloys, tungsten,tungsten alloys, other metals with a suitably high melting point, suchas refractory metals, or ceramic materials. In yet another example, theejector nozzle 108 can comprise a transparent material 114 and a layerof optical absorption material 116, similarly as described above for theejector conduits 106 of FIG. 2 , while the remaining portion of theejector conduit 106 can comprise a single material or differentcombination of materials than is employed in the ejector nozzle 108. Theterm “refractory metal” as used herein is defined to include theelemental refractory metals and alloys thereof, including, for example,niobium, molybdenum, tantalum, tungsten, rhenium, titanium, vanadium,chromium, zirconium, hafnium, ruthenium, rhodium, osmium, iridium andalloys of any of these metals, such as alloys of two or more of any ofthe refractory metals listed herein or alloys of one or more of therefractory metals with other metals, such as iron, nickel, copper,silver or others. Suitable refractory metal alloys are known in the art.

FIG. 5A illustrates a configuration of an ejector conduit 106 that canbe employed in any of the printer jetting mechanisms 100 describedherein, according to an embodiment of the present disclosure. Theejector conduit 106 of FIG. 5A comprises at least one window 108 apositioned proximate a top portion of the ejector nozzle 108. The atleast one window 108 a allows radiant energy 112 from radiant energysources 110 to be transmitted therethrough to be absorbed by a portionof print material 104 positioned proximate to the at least one window108 a. FIG. 5A shows a cross section of the conduit 106 with a window108 a on two opposing sides of the ejector nozzle 108. In an embodiment,the windows 108 a can be two separate windows positioned on opposingsides of ejector nozzle 108 that are of sufficient size to allow in adesired amount of radiant energy 112. In another embodiment, the ejectornozzle 108 of FIG. 5A can include a single window 108 a that extendsaround the entire circumference of the ejector nozzle 108. In anotherembodiment (not shown) a single window 108 a can be positioned on oneside of the ejector nozzle 108 with no window positioned on the opposingside of the ejector nozzle 108. Other configurations of windows 108 aare possible so long as they allow sufficient transmission of radiantenergy 112 at the desired position of nozzle 108 so as to provide amotive force for ejecting print material 104 b from the ejector nozzle,as will be described in more detail below. The at least one windows 108a comprises a material that is transparent to the radiant energy 112,such as fused silica or sapphire, or any of the transparent materials114 described herein. A lower portion 108 b of the ejector nozzle 108can comprises an opaque material. Examples of such opaque materialsinclude any of the refractory materials listed herein that are opaque,such as graphite, platinum, platinum alloys, tungsten, tungsten alloys,other suitable metals, such as refractory metals, or ceramic materials.In an alternative embodiment, where it is desired that print material inthe entire nozzle be heated, the at least one window 108 a can extendthe entire length of the nozzle 108. In yet another embodiment, where itis desired that print material in only a lower portion of the nozzle beheated, the at least one window can be positioned lower in the nozzle,such as at or near the tip of the nozzle 108, rather than proximate atop portion of the ejector nozzle 108 as is shown in FIG. 5A. In such anembodiment, the nozzle 108 can comprise opaque material above and/orbelow the window, such as any of the opaque materials described herein.

In an embodiment, as will be described in greater detail below, theprint material 104 that is proximate the at least one window 108 a isheated (e.g., from a liquid to a gas) by absorption of radiant energy112 to provide the desired expansion and jetting of the print material104 from the ejector nozzle 108. The length, Lw, of window 108 can beany desired length that will allow sufficient transmission of radiantenergy 112 to heat and vaporize a desired amount of the print material104 so as to drive ejection of the print material from the ejectornozzle 108. Examples of suitable values for L_(w) are about 5 microns toabout 1000 microns, such as about 5 microns to about 500 microns, suchas about 10 microns to about 100 microns, or about 15 microns to about50 microns.

In an embodiment, the outside surface of any of the ejector nozzles 108described herein can be coated with an anti-reflective coating to reducereflection of the radiant energy 112 and thereby increase absorption ofenergy, either directly or indirectly, into the print material 104.Examples of suitable antireflection coatings, such as dielectrics,including stacks of dielectrics, or other materials, are well known inthe art.

Referring to FIG. 2 , the plurality of ejector conduits 106 aresupported within an ejector housing 120. The ejector conduits 106 can beseparate structures from the housing material and can be mounted in anysuitable fashion to the ejector housing 120. In an alternativeembodiment, the plurality of ejector conduits can be integral with theejector housing 120. For example, the conduits can be formed ascapillaries or larger conduits bored or otherwise formed directly in thehousing material. The conduits can optionally be coated to provide aninner surface of the ejector conduits 106 comprising a material that isdifferent from, but integral with, the ejector housing 120. Techniquesfor forming such conduits directly in the housing material, as well astechniques for coating the conduits, are generally well known. Inembodiments, the ejector conduits 106 can comprise a different materialor the same material as the ejector housing 120.

The ejector housing 120 comprises any suitable materials that canwithstand jetting process temperatures and that can provide the desiredsupport for the ejector conduits 106. Examples of suitable housingmaterials include materials chosen from metals, such as aluminum,copper, brass and steel, refractory metals, ceramics, other refractorymaterials, polymers that are capable of withstanding processtemperatures (e.g., polymers with melting points of 150° C. to 650° C.or higher, such as 200° C. to 300° C.) and combinations thereof, such asmetal coated ceramics and ceramic coated metals. An example of acomposite housing material is copper clad with a ceramic, such asmullite, where the copper and mullite have similar thermal expansioncoefficients. The specific material employed will depend on the printmaterial to be jetted.

The ejector housing 120 comprises an inlet 122 where a portion of thehousing wall is removed to allow the radiant energy 112 from radiantenergy sources 110 to strike the ejector nozzle 108 of each of theplurality of ejector conduits 106. As an example, such an inlet 122 isindicated by the dotted lines in FIGS. 1, 2 and 4 . For instance, inFIG. 1 , the region below the dotted line is an opening in the ejectorhousing that is the inlet 122.

The radiant energy sources 110 can be any suitable radiant energysources that provide the desired thermal energy for the expansion of theprint material 104 in a relatively short amount of time. In an example,the radiant energy sources 110 are lasers. Examples of suitable types oflasers include fiber lasers; modulated lasers; scanning lasers andscanning, modulated lasers, as well as others. As illustrated in FIGS. 2and 4 , the radiant energy sources 110 can be positioned on one, two ormore sides of the array and are positionable so as to be capable ofstriking the ejector nozzles 108 of each of the plurality of ejectorconduits during operation of the printer jetting mechanism 100. Whileradiant energy sources 110 are shown positioned so that radiant energy112 from one radiant energy source strikes each ejector nozzle, multipleradiant energy sources can be positioned to strike each ejector nozzle108 through one or more inlets 122 if it is desirable to provideincreased thermal flux to the print material 104. The radiant energysources 110 have sufficient power to heat print material 104 in theejector nozzles 108 and cause the print material 104 to expandsufficiently rapidly so as to provide sufficient momentum to eject, orjet, at least a portion of the print material from the ejector nozzles108. The rapid expansion of the print material that results in thedesired ejection of the print material, also referred to herein asjetting, may or may not include heating to cause a phase change of theprint material, as will be described in greater detail below.

In an embodiment, at least a portion of the ejector housing 120comprises a reflective surface 124. The reflective surface can surroundthe inlet 122 so as to reflect radiant energy 112 toward the ejectornozzle 108 during printing. This can allow for more efficient and/ormore uniform heating and/or expansion of the print material 104.

In an embodiment, the ejector housing 120 comprises a heater mechanism126 for heating at least a portion of the ejector housing 120surrounding the ejector conduits 106 during operation of thethree-dimensional printer. The heater mechanism 126 is separate from theplurality of radiant energy sources 110. The heater mechanism 126 canprovide sufficient thermal energy so as to bring the print material 104to at or just below a desired print material expansion temperature. Forexample, in cases where expansion to provide ejection momentum of theprint material does not involve a phase change, then heater mechanism126 can provide sufficient thermal energy so as to bring the printmaterial 104 to at or just above the melting temperature. Alternatively,in the case of a phase change expansion to provide momentum of the printmaterial for ejection, heater mechanism 126 can provide sufficientthermal energy so as to bring the print material 104 to a temperaturethat is at or just below the melting temperature or vaporizationtemperature of print material 104, as desired. In an embodiment wherephase change of the print material occurs, by controlling the printmaterial temperature near the ejection site, heat loss away from theejector nozzle 108 (e.g., the melt zone or vaporization zone) can bereduced because the phase change is an isothermal process. Inembodiments where the print material 104 is a solid prior to phasechange, temperatures lower than the melting temperature can be desirableto ensure resolidification of non-ejected material before the nextejection event.

Heater mechanism 126 can comprise, for example, any suitable type ofresistive heater, inductive heater, radiant heater or combination of anyof these. For instance, heater mechanism 126 comprises heating elementsthat are embedded in or positioned proximate to the conduits 106 and/orthe ejector housing 120, such as illustrated in FIGS. 2 and 4 . Theheating elements can be in the form of resistive heating coils orinduction coils, as examples. As an example, a suitable resistive heatermechanism comprises an ohmic meander trace embedded in the ejectorhousing 120 or ejector conduits 106 surrounding the passageway 106C. Theterm “ohmic meander trace,” as used herein, refers to a conductiveheating element that has a non-linear path along a longitudinal axis(e.g., a wire suitable for resistive heating having a zig-zaging,winding or otherwise curved path). The heater mechanism 126 is separatefrom the plurality of radiant energy sources 110.

In an embodiment, the array of ejector conduits 106 includes M columnsof ejector conduits arranged on an X axis and N rows of ejector conduitsarranged on a Y axis, where M is an integer ranging from 2 to 1000 and Nis an integer ranging from 1 to 2. For example, M is 3 and N is 1 forthe array of FIG. 2 , while M is 3 and N is 2 for the array of FIG. 9 .In other examples, M is an integer ranging from 5 to 1000, 50 to 1000,or 100 to 500.

In an embodiment, the rows of the ejector conduits 106 are arrangedlinearly and the ejector conduits 106 in each row are staggered withrespect to the ejector conduits of adjacent rows, to facilitate closerpacking, as shown, for example, in FIG. 4 . In an alternative embodiment(not shown), the columns of the ejector conduits 106 are arrangedlinearly and the ejector conduits 106 in each column are staggered withrespect to the ejector conduits of adjacent columns.

In an embodiment, the ejector conduits 106 include one or more vents130, such as illustrated in FIG. 6 . Vents 130 can be positioned in orjust above ejector nozzles 108. The vents allow air or other ambient gas(as illustrated by arrow 132) to flow from outside the ejector conduits106 into the ejector conduits 106 and/or into the ejector nozzles 108 asthe print material 104 is ejected therefrom. This can allow the printmaterial being ejected from ejector nozzles 108 to more easily beseparated from the remaining print material 104 in ejector conduit 106and/or more easily be ejected from the ejector nozzles 108. The one ormore vents 130 can be in any form that will allow ambient gas to flowinto the nozzle as the print material 104 is ejected. FIGS. 7A and 7Billustrate another example in which the vents 130 take the form ofgrooves on the inner surface of the ejector nozzles 108. Any othersuitable vent configurations could be employed. In an embodiment, thevents 130, such as in FIGS. 6, 7A and 7B have dimensions that aresufficiently small so that the surface tension of liquid print material104 would not allow substantial amounts of the print material to flowout of the ejector conduits through the vents 130, while beingsufficiently large to allow ambient gas to flow through the grooves andinto the ejector nozzle 108. For example, the width and/or length of thevent 130 of FIG. 6 or diameters, in the case of circular shaped vents(not shown), or groove widths of FIG. 7 can be ten or more times smallerthan the inner width (e.g., diameter) of the ejector nozzle so thatpenetration of the liquid print material is reduced or eliminated. Thevents can be formed by any suitable means, such as by etching techniquesor laser ablation that are well known in the art.

The present disclosure is not intended to be limited to any specificdroplet jetting and/or detaching modes. For example, while the dropletscan neck off and detach at a detachment zone inside the ejector conduits106, it is also possible that the droplets can neck off and detachoutside the ejector conduits 106, followed by retraction of undetachedprint material 104 back into the ejector conduit 106. Thus, a mode ofjetting of droplets can include expansion “extrusion” of the moltenprint material 104 out from the ejector nozzle 108 into free spacefollowed by a deacceleration/retraction of the extruded print material104 as the heating pulse is terminated and the print material 104cools/contracts. Other modes of jetting and/or detaching droplets canalso be realized.

In an embodiment, ejecting at least a portion of the print materialcomprises flowing a sheath gas proximate the ejector nozzles, the sheathgas comprising one or both of an inert gas and a reducing gas. Anexample of employing a sheath gas is illustrated by the arrows 210 inFIG. 10 . The sheath gas flow can be accomplished in any suitablemanner, such as, for example, by flowing the sheath gas through sheathgas vents 212 positioned in the ejector housing 120. In an embodiment,the sheath gas is maintained at a desired temperature so as to avoidcooling the print material prior to deposition. For example, the sheathgas temperature can be at or above the melting point of the printmaterial. In this manner, the print material can be maintained in amolten state until deposition on the substrate occurs, if desired. In anembodiment, the sheath gas can be moving at approximately the samevelocity, and in approximately the same direction, as the droplets whenthey are ejected.

The printer jetting mechanisms 100 described herein can be employed inany type of printer that is suitable for jetting of a print material. Inan embodiment, the printer is a three-dimensional (“3D”) printer usablefor printing 3D objects. A block diagram of an example 3D printer 150 isshown in FIG. 8 . The 3D printer 150 can comprises any of the printerjetting mechanisms 100 comprising an array 107 of ejector conduits 106,as described herein. Additionally, the 3D printer can comprise apositioning system 152 for controlling the relative position of thearray 107 with respect to a print substrate 154. The phrase “controllingthe relative position of the array 107 with respect to the printsubstrate 154” means that either one or both of the array 107 and theprint substrate 154 can be moved in order to alter the relative positionof the array with the print substrate. The relative position of thearray 107 with the print substrate 154 is modified during printing sothat the print substrate 154 is positioned to receive print material 104jettable from the plurality of ejector conduits and thereby form a 3Dobject. The positioning system 152 can comprise one or both of a printsubstrate handling mechanism 156 for positioning the print substrate 154and an array positioning mechanism 158 for positioning the array 107 andoptionally other parts of the printer jetting mechanism 100, such as theplurality of radiant energy sources 110. The print substrate 154 cancomprise any substrate on which it is desirable to print athree-dimensional object. An example of a print substrate 154 is a buildplate that is part of the 3D printer 150, or other temporary substratefrom which the 3D object may be removed after printing. In anotherexample, the print substrate 154 may be intended to be permanentlyattached to the three-dimensional object after printing, such as, forexample, if the print substrate 154 is a printed circuit board on whicha portion of a circuit is being printed.

The print substrate handling mechanism 156 can be any mechanism suitablefor positioning the print substrate 154 to receive print materialjettable from the plurality of ejector conduits arranged in array 107during operation of the 3D printer 150. In an embodiment, the printsubstrate handling mechanism 156 has the ability to position the printsubstrate 154, such as a build plate or other substrate, by moving theprint substrate 154 in a direction along an x-axis, a y-axis and/or az-axis to a desired position to which the jetted print material istargeted. The array positioning mechanism 158 can be any mechanismsuitable for moving the array 107 in a direction along one or more of anx-axis, a y axis and/or a z-axis to a desired position to which thejetted print material 104 is targeted. The positioning system 152,including either or both of the print substrate handling mechanism 156and the array positioning mechanism 158, can comprise one or moreactuators 180 (FIG. 11 ) that can function as a mover for positioningthe print substrate 154 and array 107 relative to each other using, forexample, a system comprising tracks 182. Examples of suitable actuatorsinclude electric motors, piezo electric motors, hydraulic actuators, andpneumatic actuators. FIG. 11 illustrates an example of such apositioning system 152, which comprises an actuated (e.g., motorized)X-Y stage 184 for supporting the print substrate 154 and a verticaltrack system 186 on which all or a portion 100 a of printer jettingmechanism 100 can be moved using one or more actuators 180 to allow forvertical positioning. Portion 100 a of printer jetting mechanism 100 cancomprise any of the components of printer jetting mechanism 100described herein that are attached to the vertical track system 186 forvertical positioning, including the plurality of ejector conduitsarranged in an array and the plurality of radiant energy sources 110.The feeder mechanism 102 can be positioned so as not to be directlyattached to the vertical track system 186 (as illustrated in FIG. 11 ),or in other embodiments, can be directly attached to the vertical tracksystem 186.

As mentioned, the positioning system 152 can comprise one or both of theprint substrate handling mechanism 156 and the array positioningmechanism 158. As an example, the print substrate handling mechanism 156can be used to move the print substrate 154 along both the x-axis and yaxis, and the array positioning mechanism 158 can be used to move thearray 107 and optionally the entire printer jetting mechanism 100 or anyportion thereof along the z-axis, thereby allowing the print substrate154 and array 107 to be positioned relative to each other inthree-dimensions during operation of the 3D printer. As an example, forpurposes of this discussion, the x-axis and z-axis are as illustratedrelative to a printing operation in FIG. 10 , with the y-axis (notshown) being in the direction into the paper; the x-axis and y-axisbeing parallel to the upper surface of the print substrate 154 and thez-axis being perpendicular to the upper surface of the print substrate154. In an embodiment, the print substrate 154 is a build plate andoptionally employs a heating mechanism 155 that is capable of heatingthe build plate to desired deposition temperatures. Suitable buildplates, including build plates with heating mechanisms, are well knownin the art.

Methods of Jetting Print Material

An embodiment of the present disclosure is directed to a method forjetting print material from a printer jetting mechanism. As described at200 of FIG. 9 , the method comprises supplying a print material 104 to aplurality of ejector conduits 106 arranged in an array. The ejectorconduits 106 comprise first ends 106A configured to accept the printmaterial and second ends 106B comprising ejector nozzles 108. Theejector nozzles 108 can have an inner width (e.g., diameter) ranging,for example, from about 10 microns to about 1000 microns, or any of theother ejector nozzle inner widths disclosed herein. In the methodsdescribed herein, ejector nozzles 108 are illuminated with radiantenergy 112 to provide thermally induced expansion and ejection of theprint material as will be discussed in greater detail below.

As shown at 202 of FIG. 9 , the print material 104 is advanced in one ormore of the ejector conduits 106 of the array until the print material104 is disposed in the ejector nozzles 108 of the one or more ejectorconduits 106. In an embodiment, the print material 104 comprises aplurality of filaments. An individual filament of the plurality offilaments can be advanced to each of the one or more ejector conduits106 to supply print material at a desired feed rate. The desired feedrate can be different for each filament depending on the rate at whichthe print material is being ejected from the associated ejector nozzles108, which in turn will depend on the number of ejections per unit timefrom each nozzle and the droplet size per ejection.

The droplet size per ejection can be selected based on various factors,including the desired size of details in the object to be printed, theparticular properties of the print material (e.g., thermal transfer andexpansion properties), power of the radiant energy source, nozzle sizeand so forth. Droplets may generally have a diameter size that is assmall as the inner diameter of the ejection nozzle 108 but couldpotentially have significantly larger diameters if longer lengths offilament are heated during a single ejection. When determining theamount of print material to be heated for each ejection, the trade-offsbetween power and droplet size can be considered. In particular, alonger length of filament can be heated with proportionally higherpower, enabling a larger length of print material to be ejected. In anembodiment, the length of print material heated per pulse is about 1times to about 10 times the inner width of the print nozzle 108 (whichmay be about the same as the filament width, d_(p), (e.g., filamentdiameter) in the case where solid filaments are being fed directly intothe print nozzle) each time the print material is jetted. Thus, as anexample, the filament can be stepped forward from about one filamentwidth per laser pulse to about 10 filament widths per laser pulse, thelaser pulse melting each length of the filament as it is steppedforward.

While the cross-sectional shape of the print material 104 is illustratedin FIG. 3 as being a circle having a diameter, d_(p), it is noted thatfilaments having any other cross-sectional shape, such as, for example,a polygon, rectangle, oval or other shape, can be employed as the printmaterial 104. The cross-sectional shape of the solid filaments can bethe same as that of the cross-sectional shapes of the ejector nozzles108 (e.g., with smaller dimensions to allow feeding of filaments throughthe nozzle). Alternatively, the solid filaments can have a differentcross-sectional shape than the cross-sectional shapes of the ejectornozzles 108. For purposes of the present disclosure, the filament width,d_(p), for cross-sectional shapes other than a circle is the widestcross-sectional dimension (e.g. the diagonal between two oppositevertices of a square cross-section), where the cross-section is in aplane that is perpendicular in all directions to the longitudinal axisof the filament. Although “filament width” is sometimes referred to as“diameter” herein, the term “diameter” can be replaced by “width” whendiscussing the filament's diameter throughout this disclosure.

As shown at 204 of FIG. 9 , the print material 104 positioned in atleast one of the ejector nozzles 108 is heated by radiant energy 112,thereby causing the print material 104 to expand so as to providesufficient momentum to eject at least a portion of the print materialfrom the at least one of the ejector nozzles. This process can includethe print material 104 undergoing a phase transition from a first phaseto a second phase to achieve the desired expansion. In one example of aphase change expansion, filaments are supplied as print material 104 insolid phase to the ejector nozzles 108. The heating of the printmaterial 104 positioned in the ejector nozzles 108 melts the individualfilaments using a single pulse of radiation 112 from radiant energysources 110 to provide the desired momentum of the print material forejection. In another example of a phase change expansion, print material104 is supplied as a liquid phase to the ejector nozzles 108. Theheating of the print material 104 positioned in the ejector nozzles 108vaporizes at least a portion of the liquid print material 104 using asingle pulse of radiation 112 from radiant energy sources 110 to providethe desired momentum of the print material for ejection. In yet anotherembodiment, the print material 104 is supplied to the ejector nozzle asa liquid and expanded without changing phase to eject the liquid fromthe ejector nozzle 108. The print material 104 is expanded sufficientlyrapidly using a single pulse of radiation to provide the desiredmomentum of the print material for ejection.

The pulse length of the radiant energy 112 can be any duration that willprovide the desired expansion and cause print material 104 to beejected. Examples of suitable pulse lengths range from about 0.1microsecond to about 100 milliseconds, or about 1 microsecond to about1000 microseconds, or about 1 microsecond to about 100 microseconds.This rapid heating to phase transition causes the print material toexpand axially inside the ejector nozzle 108 so as to provide sufficientmomentum to the print material 104 to eject at least a portion of theprint material from the ejector nozzle 108. In addition to allowing forsufficient momentum for ejection, the rapid heating can also potentiallyallow for a rapid ejection rate (e.g., multiple ejections of printmaterial per second from the same ejector nozzle). While achieving theexpansion of print material 104 using a single pulse of radiation istaught above, it may also be useful to use more than one radiation pulseto achieve expansion, either from the same or multiple radiant energysources, as long as the expansion of the print material occurs quicklyenough to achieve the desired momentum of the print material forejection from the ejector nozzle to occur. For example, 2, 3 or morerapid pulses can be employed to achieve the desired expansion of theprint material as opposed to a single longer pulse.

After ejection of the print material 104, additional print material canbe advanced into the ejector nozzle or nozzles 108 and then the heatingto phase change process is repeated to eject additional print material.This process of advancing the print material and heating the printmaterial can be repeated any number of times as desired for each of theejector nozzles 108 in the array until the printing is complete. Duringthe printing, the heating and ejection of print material 104 can occurfrom a single ejector nozzle 108 in the array at a time, simultaneouslyfrom two or more ejector nozzles 108, and/or simultaneously from all ofthe ejector nozzles 108 in the array, as desired to accomplish theparticular printing process being carried out.

Any print material that expands sufficiently during phase change tocause sufficient momentum for ejection can be employed. In an example,the print material comprises at least one substance chosen from a metal,such as tin, tin alloys, lead, lead alloys (e.g., solder comprising oneor both of tin and lead), aluminum, aluminum alloys (e.g., 1000 series,2000 series, 3000 series, 4000 series, 5000 series, 6000 series, such as6061 and 6063, and 7000 series aluminum alloys), iron, iron alloys(e.g., steel), copper, copper alloys (e.g., zinc), nickel, nickelalloys, titanium, titanium alloys, tungsten, tungsten alloys, silver andsilver alloys; a polymer and a metal oxide (e.g., doped or undopedsilica, such as glass). Suitable alloys of the above named elementalmetal print materials (e.g., nickel, titanium, tungsten, silver and soforth) are well known in the art. In an embodiment, the print material104 has a metal content of greater than 90% by weight, such as about 95%to 100%, or 98% to 100%, or 99% to 100%, or 99.5% to 100%, or 9.8% to100% by weight, or 99.9% to 100% by weight. In an embodiment, the printmaterial 104 has a resistivity of less than 1×10⁻⁶ ohm·m at 20° C., suchas about 1×10⁻⁷ ohm·m to about×1×10⁻⁸ ohm·m at 20° C. (e.g., iselectrically conductive at room temperature (20° C.)).

Any of the print materials described herein can be in the form of aplurality of solid or liquid filaments. In the case of solid filaments,the width, d_(p), of the individual filaments are optionally chosen tobe slightly smaller, or substantially the same as, the inner width,d_(i), of the ejector nozzle 108, in which the individual filament ispositioned so as to provide a close fit around the individual filamentwhile still allowing the filament to be positioned within the ejectornozzle 108. The fit is sufficiently close so that when the portion ofthe filament inside the ejector nozzle undergoes expansion, the printmaterial expands in an axial direction at a rate that is sufficient toeject at least a portion of the filament material out of the ejectornozzle 108. As an example, the filament width (e.g., diameter), d_(p),is 0 to about 4% smaller than the ejector nozzle width (e.g., diameter),d_(i), such as about 0.1% to about 3% smaller, or about 0.5% smaller toabout 1.5% smaller. The relative sizing of d_(p) and d_(i) may depend onvarious factors, such as the expansion properties of the print materialduring phase change, the desired momentum of the print material uponejection, the rate of heating of the print material in the ejectornozzle and other things. As additional examples, the filament width(e.g., diameter), which can be either for a liquid filament or a solidfilament, is about 0.01 micron to 20 microns smaller than the nozzleinner width (e.g., diameter), such as about 0.1 micron to about 10microns, or about 1 micron to about 5 microns, or about 0.1 micron toabout 2 microns, or about 0.1 micron to about 1 micron smaller than thenozzle inner width (e.g., diameter).

Print material can have widths (e.g., diameters) ranging from about 10microns to about 1000 microns, from about 20 microns to about 500microns, from about 50 microns to about 200 microns, or about 100microns. Print material (e.g., solid or liquid filaments) withrelatively small widths (e.g., diameters) can have the advantage offaster heating through the entire thickness because thermal diffusivitydetermines the heat propagation time from the periphery of the filamentto the center. The ability to heat and expand the entire thickness of afilament in short bursts can allow for increased control of ejectionmomentum and/or ejection amounts (e.g., droplet sizes), among otherthings. Small diameters may also allow for smaller discrete jettableamounts of print material (e.g., smaller droplet sizes ejected fromejection nozzles 108). Therefore filaments with relatively smalldiameters may be preferable for these reasons. Desired small diametersizes will depend on the thermal diffusivity properties of the printmaterial as well as other factors. In an embodiment, the print materialwidth (e.g., solid or liquid filament diameter) ranges from about 10microns to about 100 microns, such as about 10 microns to about 50microns, or about 10 microns to about 25 microns. The inner widths(e.g., diameters) of the ejector nozzles can be sized as described aboveso as to provide a close fit around the individual filaments while stillallowing the filaments to be positioned within the ejector nozzles.

During heating using the radiant energy, any radiation from the radiantenergy sources 110 that would otherwise not strike the print material104 can be directed towards the print material 104 by refraction intransparent material 114 of the ejector conduits 106 and/or reflectionfrom the reflective surfaces 124 of ejector housing 120, as describedabove. In an embodiment, a laser beam that is wider than the filamentdiameter can be employed. The excess portion of the laser beam that doesnot directly strike the print material 104 can be refracted and/orreflected onto the print material so as to more uniformly heat theentire surface of the print material.

In embodiments where the radiant energy 112 is to be absorbed directlyby the print material 104 (as opposed to being absorbed, for example, bya layer of thermal absorption material 116), the print material 104 canbe provided (either by an in-line process or as-manufactured) with amodified surface that increases absorption at the radiant energywavelength (e.g., the laser wavelength) compared to the same printmaterial without the modified surface. This could include modifying thecolor of the filament surface to reduce reflection, applying anantireflective coating to a solid filament and/or treating the filamentsurface in some other manner. As an example, anodic etching of thesurface of a solid print material 104 is one treatment method that canbe used to increase radiation absorptivity. Anodic etching may beparticularly useful for increasing absorptivity of highly reflectivesolid metal filaments. Note that it is possible that an anodized surfacemay lose its absorptive ability before the radiant energy is fullyabsorbed. Employing such filaments as the print material in the methodsof the present disclosure may help to increase the speed of expansion ofthe print material, which in turn, may increase the deposition rate ofthe print material being jetted. In an example, the modified surface canabsorb about 90% to 100% of the incident illumination at the wavelengthof the radiant energy.

In embodiments, the print material 104 is supplied to the ejectorconduits as either a liquid or a solid and is ejected from the ejectornozzles 108 as a liquid in the form of droplets. The droplets canoptionally have a relatively small droplet size, which can allow forprinting of fine details. As examples, droplet diameters can range fromabout 0.001 mm to about 0.2 mm, about 0.005 mm to about 0.1 mm, andabout 0.01 mm to about 0.05 mm. Droplets with larger diameters can alsopotentially be formed if desired.

In another embodiment, the print material 104 is supplied to the ejectornozzles 108 as a first phase that is a liquid and then a portion of theprint material is heated to a second phase that is a vapor. Referring toFIGS. 5A and 5B, in such a process, at least a portion of thepassageways 106C prior to the ejector nozzles 108 are filled with moltenprint material (e.g., any of the print materials described herein). Allor a portion of passageways 106C can optionally be tapered, as describedherein. Using radiant energy 112 from radiant energy sources 110, whichis transmitted through the at least one window 108 a, a first portion104 a of the molten print material 104 proximate window 108 a isvaporized by rapid heating in the ejector nozzles 108 while a secondportion 104 b that is between the first portion 104 a and a tip of theejector nozzle 108 remains a liquid. The vaporized portion 104 a ofprint material 104 expands axially to provide motive force that issufficient to eject the liquid second portion 104 b of the printmaterial from the ejector nozzles 108. In an embodiment, the printmaterial 104 can initially be supplied as a solid to the first ends 106Aof ejector conduits 106 using the feeder mechanism 102, melted prior tointroduction into the ejector nozzles 108, such as by using heat from aheater mechanism 126, then vaporized by rapid heating in the ejectornozzles 108 to provide the desired motive force for jetting.Alternatively, the print material 104 can be supplied as a liquid to thefirst ends 106A of ejector conduits 106 using the feeder mechanism 102,maintained as a liquid using heat from heater mechanism 126, thenvaporized by rapid heating caused by radiant energy 112 striking theejector nozzles 108 to provide the desired motive force for jetting.

In embodiments where the print material 104 is a solid and then is phasechanged to a liquid, controlling the print material temperatures so asto be lower than the melting temperature directly after each ejectioncan be desirable to ensure resolidification of non-ejected materialbefore the next ejection event.

The method of the present disclosure can be employed to deposit printmaterial 104 from any number of ejector conduits 106 simultaneously orseparately as desired. It can also allow for the deposition of smallamounts of material from any one ejector nozzle 108 while stillproviding for a relatively high overall deposition rate due to thepotentially large number of ejector conduits 106 in the array and thepotential rate of ejection from each ejector conduit 106.

The printer jetting mechanisms for jetting print material describedherein can be employed in various printing methods. For example, any ofthe printer jetting mechanisms described herein can be employed in amethod of three-dimensional printing in which print material 104 isejected from the ejector nozzles 108 and deposited onto a printsubstrate 154, such as a build plate. One or both of the print substrate154 and the array 107 of ejector nozzles 108 can move relative to eachother in three dimensions during printing (e.g., in directions along anx-axis, y-axis and z-axis), in any manner as described herein, therebyforming a 3D object. As is well known in the art, 3D printing comprisesprinting multiple droplets or layers of material, where each droplet orlayer can be stacked one on the other, until a desired thickness of the3D object is realized. FIG. 10 illustrates an example of a printerjetting mechanism 100 comprising a plurality of ejector conduits 106simultaneously ejecting droplets 200 to print a 3D object 202 on a printsubstrate 154. Many layers 204 of droplets 200 may be deposited, onelayer or droplet on the next, until the 3D object is completed. As wouldbe readily understood by one of ordinary skill in the art, the dropletsand/or layers can be stacked in any desired order, so that, for example,a first underlying layer 204 may or may not be completed beforebeginning subsequent layers and there may or may not be a recognizablelayering pattern to the order of material deposition. Rather, thedroplets, layers and/or portions of layers can be stacked in any desiredorder to complete the 3D object

The following examples are illustrative only and are not meant to, nordo they, limit the scope of the invention as set forth in the claims.

PROPHETIC EXAMPLES

Example 1: Solid to Liquid Phase Change Expansion: One each of aluminum,copper and iron wires having diameters of 0.0001 meters are held justbelow the melting temperature and each fed into a separate refractorytube (e.g. fused silica tube) with an inner diameter just larger thanthe outer diameter of the wires. A laser pulse is absorbed by a 0.0001meter end portion of each wire and melts the wire portion inmicroseconds. During melting, the expansion of the molten wire materialoccurs primarily along the direction of the silica tubes longitudinalaxis. The free meniscus of the molten material accelerates axially inthe tube and the molten region accelerates at approximately half therate of the meniscus. The acceleration of the molten material in thetube, as shown in Table 1 below, corresponds to an energy well above theenergy it takes to detach a droplet of the molten material from the wireand eject it from the tube, thus resulting in a droplet of moltenmaterial being jetted from the tube. The energy employed to melt asufficient portion of the wire for jetting is supplied by a laser thatis capable of pulsing at the desired pulse power, such as a fiber laseror scanned, modulated laser.

The calculations in Table 1 below assume no volume between the wire andthe tube. The calculated motive force=Average Acceleration of the melttimes the mass of the melt. The “pulse energy” in the table refers tothe energy to melt the wire length and could potentially be supplied bya single laser pulse.

TABLE 1 Wire Properties Units Al wire Cu wire Fe wire T_(melt) C. 6601084 1150 Density kg/m³ 2700 8960 7870 ρ_(m) Latent heat kJ/kg 396 206247 Λ Specific latent kJ/m³ 1.07E+06 1.85E+06 1.94E+06 λ heat Thermal6.50E−02 5.30E−02 3.50E−02 ε expansion on melt Mass kg 2.12E−09 7.04E−096.18E−09 m = ρπd²l/4 Diameter m 0.0001 d Length m 0.0001 l Melting ofwire in Silica Tube Elongation of m 6.50E−06 5.30E−06 3.50E−06 Δl = εlwire material in silica tube due to melt Pulse length s 5.00E−06 t_(p)of laser Meniscus m/s 1.30 1.06 0.70 velocity of melt in Tube Meniscusm/s² 2.60E+05 2.12E+05 1.40E+05 a = Δl/t_(p) ² Acceleration in TubeAverage m/s² 1.30E+05 1.06E+05 7.00E+04 a_(m) = 0.5a acceleration inTube Motive force N 8.78E−05 2.37E−04 1.38E−04 F = ma_(m) Pulse energy J8.40E−04 1.45E−03 1.53E−03 E = mΛ for melt Pulse power W 1.68E+022.90E+02 3.05E+02 P = E/t_(p)

Example 2: Liquid to Liquid Expansion: One each of aluminum, copper,iron and indium wires having diameters of 0.0001 meters are fed into aseparate refractory tube (e.g. fused silica) with an inner diameter justlarger than the outer diameter of the wires. Liquid metals such asmercury (Hg), gallium-indium or gallium-indium-tin eutectic mixtures arefed into a similar silica tube. For the wires materials, at least aportion of each wire is melted and maintained as a liquid proximate theend of the silica tube, so that the meniscus of the liquid is positionedat the end of the graphite tube. Then a laser pulse is absorbed by a0.0001 meter end portion of each silica tube to heat the liquid materialtherein so as to increase the temperature by about 300 Kelvin in about 5microseconds. During heating, the expansion of the liquid materialsoccurs primarily along the direction of the silica tubes longitudinalaxis. The free meniscus of the molten material accelerates axially inthe tube and the molten region accelerates at approximately half therate of the meniscus. The acceleration of the molten material in thetube, as shown in Table 2 below, corresponds to an energy above theenergy it takes to detach a droplet of the molten material from theliquid and eject it from the tube, thus resulting in a droplet of moltenmaterial being jetted from the tube. The energy employed to heat asufficient portion of the material for jetting is supplied by a laserthat is capable of pulsing at the desired pulse power.

For the calculations in Table 2 below, motive force=Average Accelerationof the liquid times the mass of the liquid. The “pulse energy” in Table2 refers to the energy to raise the temperature of the liquid by 300Kelvin and could potentially be supplied by a single laser pulse.

TABLE 2 Wire/Material Properties Units Al Wire Cu Wire Fe Wire Hg InT_(melt) C. 660 1084 1150 157 Density kg/m3 2700 8960 7870 13600 7100 ρμSpecific heat kJ/kg-K 1.18 0.49 0.82 of melt J/kg-K 1180 490 820 140 230c. Thermal 1/K 1.34E−04 1.12E−04 9.20E−05 1.80E−04 1.00E−04 βexpansivity of melt Diameter m 0.0001 d Length m 0.0001 l Mass kg2.12E−09 7.04E−09 6.18E−09 1.07E−08 5.58E−09 m = rpd2l/4 Molten materialheating and expansion in silica tube Temperature K 300 ΔT riseElongation 4.02E−02 3.36E−02 2.76E−02 5.40E−02 3.00E−02 ε = βΔTElongation m 4.02E−06 3.36E−06 2.76E−06 5.40E−06 3.00E−06 Dl = el Pulselength s 5.00E−06 tp Velocity m/s 0.80 0.67 0.55 1.08 0.60 v = Dl/tpmeniscus Acceleration m/s2 1.61E+05 1.34E+05 1.10E+05 2.16E+05 1.20E+05a = Dl/tp2 meniscus Average m/s2 8.04E+04 6.72E+04 5.52E+04 1.08E+056.00E+04 am = 0.5a acceleration Motive force N 1.70E−04 4.73E−043.41E−04 1.15E−03 3.35E−04 F = mam Pulse energy J 7.51E−04 1.03E−031.52E−03 4.49E−04 3.85E−04 E = mcDT Pulse power W 1.50E+02 2.07E+023.04E+02 8.97E+01 7.70E+01 P = E/tp

Example 3: Liquid to Vapor Phase Change Expansion: One each of aluminum,copper and iron wires having diameters of 0.0001 meters are fed into aseparate refractory tube (e.g. a graphite tube) with an inner diameterjust larger than the outer diameter of the wires. At least a portion ofeach wire is melted and maintained as a liquid proximate the end of thegraphite tube, so that the meniscus of the liquid is positioned at theend of the graphite tube. The graphite tube includes a window positionedjust above a 100 micron graphite end portion of the tube. The windowcomprises a material that is transparent to light emitted from a laserused for vaporizing the liquid. The window has a dimension along thelength of the tube of about 25 microns. A laser pulse from the laser istransmitted through the window and causes the liquid material proximatethe window to vaporize in about 5 microseconds. An end portion of themolten material between the window and the tip of the graphite remains aliquid. During heating, the expansion of the vaporized material occursprimarily along the longitudinal axis of the graphite tube and forcesthe end portion of the liquid, or molten material, to accelerate axiallyso as to be ejected from the tube, thus resulting in a droplet of moltenmaterial being jetted from the tube. The energy employed to heat andvaporize a sufficient portion of the molten material for jetting issupplied by a laser that is capable of pulsing at the desired pulsepower.

For Table 3 below, the “pulse energy” refers to the energy used tovaporize a portion of the liquid as described above and couldpotentially be supplied by a single laser pulse.

TABLE 3 Wire/Material Symbol or Properties Units Al wire Cu wire Fe wireFormula T_(boil) C. 2327 2595 2862 Density kg/m3 2700 8960 7870 ρμLatent heat kJ/kg 11400 5069 6340 Λ Specific latent kJ/m3 3.08E+074.54E+07 4.99E+07 λ heat Mass kg 5.30E−10 1.76E−09 1.55E−09 m = rpd2l/4Diameter m 0.0001 d Length l 2.5E−05 l Vaporization of portion of liquidin graphite tube Pulse length s 5.00E−06 tp Pulse energy J 6.04E−038.92E−03 9.80E−03 E = mL Pulse power W 1.21E+03 1.78E+03 1.96E+03 P =E/tp

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. In addition, while a particular feature of thepresent teachings may have been disclosed with respect to only one ofseveral implementations, such feature may be combined with one or moreother features of the other implementations as may be desired andadvantageous for any given or particular function. Furthermore, to theextent that the terms “including,” “includes,” “having,” “has,” “with,”or variants thereof are used in either the detailed description and theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising.” Further, in the discussion and claims herein, theterm “about” indicates that the value listed may be somewhat altered, aslong as the alteration does not result in nonconformance of the processor structure to the illustrated embodiment. Finally, “exemplary”indicates the description is used as an example, rather than implyingthat it is an ideal.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompasses by the following claims.

What is claimed is:
 1. A method of printing a three-dimensional object,the method comprising: supplying a print material to a plurality ofejector conduits arranged in an array, the ejector conduits comprisingfirst ends configured to accept the print material and second endscomprising ejector nozzles; advancing the print material in one or moreof the ejector conduits of the array until the print material isdisposed in the ejector nozzle of the one or more ejector conduits; andheating the print material positioned in at least one of the ejectornozzles using radiant energy, the heating causing at least a portion ofthe print material to be ejected from the at least one of the ejectornozzles and onto a print substrate; repeating both the advancing theprint material and the heating the print material to form athree-dimensional object on the print substrate.
 2. The method of claim1, wherein the ejector nozzles have an inner width ranging from about 10microns to about 1000 microns.
 3. The method of claim 1, wherein theprint material comprises a plurality of filaments, and further whereinthe advancing the filaments comprises advancing an individual filamentof the plurality of filaments to each of the one or more ejectorconduits.
 4. The method of claim 3, wherein the radiant energy is alaser pulse having a pulse length ranging from about 1 microsecond toabout 100 microseconds.
 5. The method of claim 3, wherein the pluralityof filaments comprise at least one substance chosen from a metal, apolymer and a metal oxide.
 6. The method of claim 3, wherein theplurality of filaments comprise a metal having a resistivity of lessthan 1×10⁻⁶ ohm·m at 20° C.
 7. The method of claim 3, wherein theplurality of filaments comprise a solid metal having an anodizedsurface.
 8. The method of claim 3, wherein the individual filament has awidth that is about 0 to about 4% smaller than an inner width of theejector nozzle in which the individual filament is positioned.
 9. Themethod of claim 1, wherein during the heating of the print materialpositioned in at least one of the ejector nozzles using radiant energy,at least a portion of the print material undergoes a phase transitionfrom a first phase to a second phase.
 10. The method of claim 9, whereinfirst phase is a solid and the second phase is a liquid.
 11. The methodof claim 10, wherein the liquid is ejected from the ejector nozzle ofthe one or more ejector conduits as droplets having a droplet diameterranging from about 0.001 mm to about 0.2 mm.
 12. The method of claim 9,wherein the first phase is a liquid and the second phase is a gas, andfurther wherein a first portion of the print material positioned in theat least one of the ejector nozzles undergoes the phase transition whilea second portion of the print material between the first portion and atip of the ejector nozzle remains a liquid, the second portion being theportion of the print material that is ejected from the at least one ofthe ejector nozzles.
 13. The method of claim 1, wherein during theheating of the print material positioned in at least one of the ejectornozzles using radiant energy, the print material is maintained in asingle phase.
 14. The method of claim 1, wherein the heating comprisessimultaneously heating the print material positioned in the ejectornozzles of 2 or more ejector conduits.
 15. The method of claim 1,wherein the printed object is a three-dimensional object comprising aplurality of stacked layers of print material.
 16. A method for jettingprint material from a printer jetting mechanism, the method comprising:supplying a print material to a plurality of ejector conduits arrangedin an array, the ejector conduits comprising first ends configured toaccept the print material and second ends comprising ejector nozzles;advancing the print material in one or more of the ejector conduits ofthe array until the print material is disposed in the ejector nozzles ofthe one or more ejector conduits; and heating the print materialpositioned in at least one of the ejector nozzles using radiant energy,the heating causing at least a portion of the print material to beejected from the at least one of the ejector nozzles.
 17. The method ofclaim 16, wherein the ejector nozzles having an inner width ranging fromabout 10 microns to about 1000 microns.
 18. The method of claim 16,wherein the print material comprises a plurality of filaments, andfurther wherein the advancing the filaments comprises advancing anindividual filament of the plurality of filaments to each of the one ormore ejector conduits.
 19. The method of claim 18, wherein the radiantenergy is a laser pulse having a pulse length ranging from about 1microsecond and about 100 microseconds.
 20. The method of claim 18,wherein the plurality of filaments comprise at least one substancechosen from a metal, a polymer and a metal oxide.
 21. The method ofclaim 18, wherein the plurality of filaments comprise a metal.
 22. Themethod of claim 21, wherein the plurality of filaments comprise a solidmetal having an anodized surface.
 23. The method of claim 18, whereinthe individual filament has a width that is about 0 to about 4% smallerthan an inner width of the ejector nozzle in which the individualfilament is positioned.
 24. The method of claim 16, wherein during theheating of the print material positioned in at least one of the ejectornozzles using radiant energy, the print material undergoes a phasetransition from a first phase to a second phase.
 25. The method of claim24, wherein the first phase is a solid and the second phase is a liquid.26. The method of claim 25, wherein the liquid is ejected from theejector nozzle of the one or more ejector conduits as droplets having adroplet diameter ranging from about 0.001 mm to about 0.2 mm.
 27. Themethod of claim 24, wherein the first phase is a liquid and the secondphase is a gas, and further wherein a first portion of the printmaterial positioned in the at least one of the ejector nozzles undergoesthe phase transition while a second portion of the print materialbetween the first portion and a tip of the ejector nozzle remains aliquid, the second portion being the portion of the print material thatis ejected from the at least one of the ejector nozzles.
 28. The methodof claim 16, wherein during the heating of the print material positionedin at least one of the ejector nozzles using radiant energy, the printmaterial is maintained in a single phase.
 29. The method of claim 16,wherein the heating comprises simultaneously heating the print materialpositioned in the ejector nozzles of 2 or more ejector conduits.